Vitamin D is what I use for the single camera I have now. It has a nice ability to search and return different event types - human inside an area, human entering/leaving, etc. This is very valuable if you have the camera pointed at any area which generates a lot of movement.

"You are being watched. The government has a secret system: a machine that spies on you every hour of every day. I know, because I built it. I designed the machine to detect acts of terror, but it sees everything. Violent crimes involving ordinary people; people like you. Crimes the government considered 'irrelevant'. They wouldn't act, so I decided I would. But I needed a partner, someone with the skills to intervene. Hunted by the authorities, we work in secret. You'll never find us, but victim or perpetrator, if your number's up... we'll find you".